A test failure occurred where a send stream had only a BEGIN record. This should not be possible if the send returns without error. Prevented this from happening in the future by adding an assertion to dmu_send_impl() to verify that if the function returns 0 (success) both a BEGIN and END record are present. Did this by adding flags to dmu_sendarg_t (indicating whether BEGIN or END records sent), having dump_record() set flags appropriately, adding VERIFY statement to dmu_send_impl().